Testing apparatus for electrostatic coating material



N 1958 GOHEI OSAME TESTING APPARATUS FOR ELECTRQSTATIC COATING MATERIAL Filed March 9, 195a INVENTOR. GOHEI OSA ME BY WM, act/.5.

United States Patent O TESTING APPARATUS FOR ELECTROSTATIC COATING MATERIAL Gohei Osame, Minami-ku, Osaka City, Japan Application March 9, 1956, Serial No. 570,476 Claims priority, application Japan April 2, 1955 2 Claims. (Cl. 73-150) The present invention pertains particularly to a device for a preliminary test of paint prior to the actual coating to decide beforehand whether the paint obtains the expected coating effects or not, having for its object to provide an apparatus, safe and easy to handle, for conducting on an inexpensive basis the test with the smallest amount of specimen of the paint to be used for coating.

The main feature of this apparatus broadly comprises an inductive plate for holding a specimen of paint on the groove cut on the upper surface and inclining toward the sharp edge thereof, which is electrically connected with the negative electrode of a direct-current highvoltage generator, and an earthed plate or cylinder for holding on its inner surface a recording paper, which is set in front of the outer edge of said groove.

In view of the electrostatic coating currently in use, it is to be noticed that the effect of coating varies to a great extent according to the kinds and properties of the paint used and the solvent and thinner thereof, that is to say, to the charging and atomizing conditions pertinent to the electrified field and the degree of dispersion of the atomized particles of the paint. It is further confirmed that the variation in the effect of coating cannot be ascribed simply to the inductivity, dipolarity, degree of molecular association, surface tension or viscosity of the paint used or of the components thereof. Heretofore, therefore, to decide whether a paint is good for electrostatic coating or not, there is no other way than to perform an actual test with the expensive electrostatic coating machine, necessitating much amount of paint for the test and a large-scale setup to the disadvantage of the circles concerned. It is further very inconvenient and expensive to the paint producer to conduct the actual test of this sort on respective paints with the machine requiring highly skilled operation.

According to the present invention based on the aforesaid evidence, however, the test can be easily and safely performed with a small, negligible amount of paint, enabling on an inexpensive basis both coating industry and paint producers to decide which is the most suitable sort of paint for electrostatic coating.

In order that the invention may be readily and clearly understood, the testing apparatus in accordance with the invention is illustrated by way of example in the accompanying drawing, in which:

Figure 1 is a partial section of the apparatus to show a side view thereof. Fig. 2 is a horizontal section of the apparatus. Fig. 3 is an oblique section of a disc as an example of the edged plate for holding a specimen of paint. Fig. 4 is also an oblique section of another example of said plate.

In the preferred embodiment of the invention shown in the drawings, the testing apparatus of paint for electrostatic coating comprises a direct-current high-voltage generator 1, the size of which is, for instance, 45 cm. long, 35 cm. wide and 50 cm. high, weighing about 25 kg., a high-voltage-proof pipe 2 made of insulating material 2,859,615 Patented Nov. 11, 1958 and fixed upon the generator 1, an inductive wire 3 connecting through the pipe 2 the negative electrode of the generator 1 and an inductive mount 4 which is fixed on the top of the pipe 2, and an inductive edged plate 5 for holding a specimen of paint, which is placed upon the mount 4. The specimen plate 5 is a circular plate with the bottom circumference 6 wider than the upper, provided on the upper surface with several grooves 7 radially arranged and inclined toward the bottom circumference 6, and the height of the pipe 2 is adjusted in such a manner as the specimen plate 5 placed on the mount 4 on the top of the pipe 2 occupies the central part of an earthed cylinder 8, 30 cm. in diameter and 24 cm. high, for instance, which is placed on the generator 1, holding on its inner surface a recording paper 9.

To conduct the coating test with this apparatus, pour as a specimen a drop or two of the paint to be tested upon the outer edge 6 of a groove 7, and turn on direct current of, for instance, 50,000 voltages. Then corona discharge takes place between the edge 6 of the groove 7 and the earthed cylinder 8, and the specimen-paint on the edge 6 is atomized and the atomized particles thereof disperse upon the recording paper 9.forming a pattern specific to the paint. So, then, turn off the current and take out the paper from the cylinder to study the pattern recorded thereon. It is therefore a matter of simple procedure to detect from the pattern thus obtained the size of the atomized particles, the .degree of dispersion and other qualities of the paint pertinent to electrostatic coating by comparing the pattern with other patterns previously obtained.

The power of electricity to be used in this apparatus is equal or approximate to the power of electricity to be used for actual coating, and the test can be conducted on several kinds of paint, that is, as many kinds as the number of the groove, when respective specimens are placed one by one on the outer edges of the grooves separately and turn on the switch, because respective specimens are atomized separately and form their'respective patterns on the papers separately. Instead of the circular plate 5, an inductive oblong tray resembling a pen point and provided with a groove 10 inclining toward the pointed edge 11, cut off at the end obliquely to facilitate the discharge and dispersion of the atomized particles of a specimen, as shown in Fig. 4, will be used. Instead of the cylinder 8, a metal plate or a partial arc of a cylinder will also be set in front of the outer edge 6 of the groove 7.

In the above specification I have described several modes of function of the testing apparatus of paint for electrostatic coating, and it is my intention that the invention be not limited by any of the details of description unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. An electrostatic coating material testing apparatus comprising a cylindrical drum for holding perpendicular a plurality of recording papers around the inner surface of the wall thereof, means for holding vertical said cylindrical drum, a disc having its periphery inclined at an angle of substantially degrees to the horizontal so that the bottom area of said disc is greater than the upper area, said disc having a plurality of grooves radially engraved upon the upper surface area of said disc starting from the center thereof and inclined toward the bottom area of said disc to form sharp-edged fringes withthe periphery of the bottom area for holding thereupon in predetermined volume a specimen of the liquid coating material to be tested, means for holding horizontal said disc within said recording paper holding cylindrical drum and spaced at a predetermined equal distance from v 3" the inner surface of the wall thereof so that respective sharp-edged fringes of said specimen holding grooves confront respective recording papers, 21 high potential source for, establishing an electrostaticfield between said sharp-edged fringesl of said specimen holding grooves and the..inner,surface of the Wall of said recording paper holding cylindrical drum to cause the sprays of atomized particles ofrrespective specimens to be respectively deposited upon a predetermined portion of the surface of each. of the, recording papers, forming thereupon respective, patterns specific to each of the liquid coating materials, employed, the uniformity of said patterns being dependentup0n the predetermined volume of the specimen to be, used and the distance betweenthe inner surface of therw all ,of the recording paper holding cylindrical drumtand the sharp-edged fringes of the specimen holding grooves, A

2. An electrostatic coating material testing apparatus comprising a cylindricaldrum for holding perpendicular a sheet, of recording paper around the inner wall thereof, means forholding vertical said cylindrical drum, a tray havingoneend cut off obliquely atan angle of around 75 degrees to the horizontal and having a groove extending longitudinally thereof inclined toward the bottom edge of said end to form a sharp-edged fringe at said edge fo holding thereupon in predetermined volume a specimen of the liquid coating material to be tested, means for holding said tray horizontal inside said cylindrical drum and spaced at a predetermined distance from the inner surface of the wall thereof and the recording paper thereupon, a high potential source for establishing an electrostatic field between said sharp-edged fringe and the inner surface of the wall of the recording paper holding cylindrical drum to cause the spray of atomized particles of the specimen employed to be deposited upon a predeter mined portion of the surface of the recording paper, forming a pattern specific to the liquid coating material employed, the uniformity of said pattern being'dependent upon the volume of the specimen to be used and the distance between the inner surface of the wall of the recording paper holding cylindrical drum and the sharp-edged fringe of the specimen holding groove.

References Cited in the file of this patent UNITED STATES PATENTS 

